Key Takeaways
Uninsured/Underinsured Motorist Coverage
Uninsured motorist (UM) and underinsured motorist (UIM) coverage are auto insurance protections that pay for your injuries and, in some cases, vehicle damage when the at-fault driver either has no insurance or doesn't carry enough to cover your losses. Instead of leaving you to chase an uninsured driver through civil court, this coverage steps in on their behalf. It's purchased as part of your own auto insurance policy.
UM and UIM are sometimes bundled together and sometimes sold as separate endorsements. Coverage limits, stacking rules, and whether bodily injury and property damage are split into distinct sub-coverages all vary by state law and insurer.
The Problem UM/UIM Coverage Was Built to Solve
Auto insurance is legally required in nearly every U.S. state — but legal requirements don't guarantee compliance. According to the Insurance Research Council, an estimated 1 in 8 drivers on American roads has no auto insurance. In some states, that rate climbs significantly higher.
Even among insured drivers, many carry only the state-mandated minimum liability limits. Those minimums — often $25,000 or less per person for bodily injury — can fall well short of covering a serious crash involving hospitalization, lost income, or long-term rehabilitation.
That's the gap UM/UIM coverage was designed to fill. Without it, if an uninsured driver runs a red light and injures you, your primary recourse is to sue them personally — a process that can take years and may yield nothing if the driver has no assets. UM/UIM coverage removes that uncertainty by turning the claim back to your own insurer.
1 in 8
U.S. drivers estimated to be uninsured
According to the Insurance Research Council's periodic studies on uninsured motorist rates across the country.
~$25,000
Typical state minimum bodily injury limit per person
Many states set minimum liability requirements at this level, which may not cover costs in a serious accident involving hospitalization.
20%+
Uninsured driver rate in some U.S. states
Certain states consistently record uninsured motorist rates well above the national average, according to Insurance Research Council data.
For a fuller picture of how this fits into your overall policy, see our guide to auto insurance basics.
How UM and UIM Coverage Actually Work
Uninsured motorist (UM) coverage activates when the at-fault driver carries zero insurance — including most hit-and-run situations where the driver flees the scene. You file a claim with your own insurer, who pays up to your UM policy limits for covered losses.
Underinsured motorist (UIM) coverage applies when the at-fault driver does have insurance, but their limits aren't sufficient to cover your actual damages. For example, if the at-fault driver's policy pays $15,000 but your medical bills reach $60,000, your UIM coverage can pay the difference up to your own UIM limits.
Both coverages typically come in two components:
- Bodily injury (UM/UIM BI): Covers medical expenses, lost wages, and pain and suffering for you and your passengers.
- Property damage (UM/UIM PD): Covers damage to your vehicle — though in practice, collision coverage may overlap with this depending on your policy structure.
Understanding how these interact with liability and collision coverage is important. Learn how liability, collision, and comprehensive coverage each pay out to see where UM/UIM fits in.
Match Your UM/UIM Limits to Your Liability Limits
A widely used approach is to set your UM and UIM limits equal to your liability limits. The logic: both are designed to cover the same categories of harm — medical costs, lost wages, pain and suffering — just from opposite sides of the accident. Carrying $100,000/$300,000 in liability but only $25,000/$50,000 in UM/UIM leaves a significant gap in your own protection. Ask your insurer what it would cost to align them — the difference in premium is often smaller than drivers expect.
Who Should Seriously Consider This Coverage
While UM/UIM coverage benefits virtually any driver, certain situations make it especially important:
- Drivers in high-uninsured-rate states: States like Mississippi, Michigan, and Tennessee historically have higher rates of uninsured motorists, increasing your statistical exposure.
- Commuters with heavy highway exposure: More miles driven means more interactions with other drivers — and more chances of encountering one who's uninsured.
- Drivers without robust health insurance: If your health coverage has high deductibles or gaps, UM bodily injury coverage becomes a critical backup for medical bills after a crash.
- Drivers carrying minimum liability limits: If you've chosen minimum coverage to lower premiums, you're likely also exposed on the other side. Understand the real tradeoffs between minimum and full coverage before deciding.
Even if none of these apply specifically, the relatively modest cost of adding UM/UIM coverage compared to the potential out-of-pocket exposure in a serious crash makes it worth evaluating carefully with your insurer or a licensed agent.
This article is for general informational purposes only and does not constitute personalized insurance, legal, or financial advice. Coverage terms, requirements, and availability vary by state and insurer. Consult a licensed insurance professional and review your actual policy documents before making coverage decisions.